Continuous Observational Data of Atmospheric CH4 Mixing Ratios on Hateruma Island

The present data set is time series data of atmospheric CH4 mixing ratios measured on Hateruma Island, Japan. Hateruma Island is a small ellipse-shaped island in east-west direction with an area of 13 m2, and is the southwestern-most inhabited island of the Japanese archipelago with a population of 500. The monitoring station is located at the eastern tip of the island. Air is sampled from an intake placed on a tower adjacent to the observation station about 37 m above ground level, and the CH4 mixing ratios are measured semi-continuously by using a gas chromatographic system. Hateruma is influenced by the East Asian monsoon, with northerly winds from the continent in winter and southerly winds from the Pacific Ocean in summer. Since Hateruma is a small island surrounded by seas, the influence from local emission sources is negligible.本数据集为日本波照间岛（Hateruma Island）观测得到的大气甲烷（CH4）混合比时间序列数据。该岛为东西向延展的椭圆形小岛，面积13平方米，是日本列岛最西南端的有人居住岛屿，常住人口约500人。监测站设于该岛东端。空气样品通过设于观测站旁一座离地约37米的塔架上的采样进气口采集，随后采用气相色谱系统半连续测定甲烷混合比。波照间岛受东亚季风影响，冬季盛行来自大陆的偏北风，夏季则为来自太平洋的偏南风。由于该岛为四面环海的小型岛屿，本地排放源的影响可忽略不计。